Officials are probing how a 51-year-old highway bridge came to collapse in the Italian port city of Genoa yesterday, killing at least 26 people and injuring 16 others as it sent dozens of vehicles tumbling into a heap of concrete and twisted steel.

Severe weather warning issued for parts of central and southern NSW and ACT

A severe weather warning is in place for central and southern parts of New South Wales and the ACT.

The Bureau of Meteorology said damaging winds and even blizzards are expected in Metropolitan, Illawarra, Southern Tablelands, Snowy Mountains, Australian Capital Territory and parts of the Hunter, South Coast, Central Tablelands and South West Slopes Forecast Districts.

"A trough is moving through southern and central New South Wales with vigorous westerly winds ahead of and behind it," the BOM said.

"Damaging winds averaging 60 to 70 km/h with peak gusts of 90 to 100 km/h have been observed along parts of the ranges and coastal areas.

"Damaging winds averaging 80 to 90 km/h with peak gusts of 110 km/h are forecast about the Alpine peaks overnight.

"Blizzards are possible above 1300 metres in the Alpine area lowering to 1000 metres overnight."

Thousands of homes are already without power due to gale-force winds raging across NSW and the ACT.

Damaging winds have reportedly knocked out power to more than 11,000 homes and businesses.

Ausgrid said about 1400 homes and businesses had lost power around Epping and Beecroft while Endeavour Energy is reporting power outages from the Hunter region to the South Coast.